Some pain crept back into the foot when I did an easy 10k last Monday (after the Sunday 30k) so I took 72 hours off completely just doing some biking and swimming. Saw my Chiropractor again on Thursday and he released everything again and confirmed it looks like I've avoided a stress fracture.

Did 8k gently up to mara pace on the Thursday, then 18k on Friday with last 12k steady. Honestly that last 12k was about the best I have ever felt running. HR 130-135, tapping along at 3:55-4:00/km. Yesterday (Sat) I did 5k easy and then 5x1k at mara pace (3:40-45) feeling great. Rested today (funky weekend schedule as I was attending a course).

Marathon pace looks from these workouts to be floating around 3:40-43, but I think I'm going to really concentrate on keeping the HR <140 for the first 21k, and under <150 until 30k, no matter what. The past 2 marathon's I've ended up 145-155 quite early on trying to hold pace... which has not been ending well!

Weight is still ~75kg (vs. 77-79 in previous marathons) and the cold I've had for about 3 weeks appears to be coming to an end

<76kg on the line, great weather (10-12 degrees, light wind). No foot pain or any niggles at all although did have to stop for the loo and lost about 45s, but definitely worthwhile!

Very happy with that. Stuck to the HR plan despite the paces being slower than expected (3:46 Vs 3:43 per km at 140bpm). Felt great through 21k (1:19:40) and then gradually increased the HR up to 150. Planned to go to 160+ at 30k but in the end waited until 37k before pushing (hit 174 by the end and felt like the tank was pretty well empty!).

The other thing I did differently was taking on all nutrition in the first half. I had 100cals every 5k until 21k then ran the last half only on water and felt nicely fuelled and light on my feet.

Now... break time.

After much testing (MRI etc) over the past months it's become clear I have a significantly enlarged left atrium (>40mls/m2 indexed for body surface area if interested!). Everything else with the heart & cardiovascular system is good so it's not 'dangerous' but is likely the cause of the arrythmia I had in July and could potentially lead to reccurences in the future.

Therefore have decided (with cardiologist) to be on the safe side and completely de-condition for 6-8 weeks to give it a rest (I basically haven't taken more than a couple of weeks off in 8-9yrs!) and see if we can bring the atrium back within 'normal' ranges. Given my lower weight and reduced (i.e no biking) training volume it's possible I could keep it closer to normal ranges even at high fitness level. Will be starting a proper strength/core program and am allowed 2hrs light jogging per week (<110bpm) so shouldn't be starting from absolute zero.

Anyway, will keep you posted and be back (and hopefully not fat!) ready for a new cycle building towards a spring marathon (the 2:39 gives me a good few sub-elite start options ).

Yes I can continue to swim (again <110bpm as the point is to detrain the heart) so will certainly be doing some of that as part of my weekly 2h excercise.

Yes it is 'athletes heart' and common for endurance athletes. The reason I'm being more cautious is the fact that I got an atrial fibrillation at age 34. Again these arrythmia are common in athletes (particularly tall athletes due to the enlarged atrium which causes stretching and repositioning of the signal conducting nodes) but usually once they start happening they tend to occur with increasing frequency (maybe once every few years initially, then annually and so on... many lifetime endurance athletes in their 60/70's end up in persistent atrial fibrillation).

Atrial fibrillation itself also isn't dangerous when the rest of the system is good, but with age, they greatly increase stroke risk (blood not emptied fully from atrium can form clots).

Once you have frequent occurrences you need to either take pills to steady the heart rate (which limit athletic performance) or have surgery to fix the nodes (ablation) which is best avoided for obvious reasons!

Given I've had my first afib so young (most lifetime athletes get their first in 50s) its better to get ahead of it I think!

Well... my legs have never felt so good! It's actually quite strange being able to run for the bus or catch the 2 year old without any wincing. I must have had more little niggles than I thought. My flexibility is also improving considerably.

Seriously though, all good so far at the halfway mark. I've been doing strength stuff every other day and running about 30-40k per week, nothing over 110bpm and nothing over 60mins. Usually around 5:30-6:00 per km (usually with the running buggy).

Weight is still stable around 76kg so hopefully I'll come out of this ok. Definitely looking forward to getting training again, the 'mind' is good and fresh!

Hard to say if there has been any genuine heart change yet but I think resting heart rate is trending up a little. I'll be getting all the tests in December.